Patients meeting DSM-III-R criteria for panic disorder, and nervous pointer dogs, an animal model of panic disorder, are evaluated using chemical model strategies, neuroendocrine challenge techniques, and physiological and biochemical methodologies. Particular attention is given to the role of the noradrenergic, dopaminergic, serotoninergic, adenosinergic, and cholinergic neurotransmitter or neuromodulatory systems in the pathogenesis of abnormal fear behaviors and regulation of hypothalamic-pituitary function.